Abstract

This is an investigation to analyze the effect of coal sequence on seismic amplitude. The Barail Coal Shale (BCS) sequence sands of Barail Group of Oligocene age are the main pay sands of Laplinggaon area. It was observed though the coal percentage is not varying much throughout the area, there is a large variation of average absolute amplitudes. The reasons behind this are investigated in this paper through post-stack modeling. Further investigation was also done through pre-stack modeling to assess whether fluid effects were detectable on the far-offset amplitudes within coal sequences. Also with the use of near average absolute amplitude and far amplitude, a fluid indicator attribute has been derived. The results indicated that all three factors i.e. coal proportion, number of coal layers and relative disposition of thick and thin layers within the sequence contribute to seismic amplitude variations. The higher the near average absolute amplitude, the more likely it is to have higher coal content, while increasing far amplitude means a higher likelihood of oil/gas occurrences, for low coal percentage.